Unit 1 - Energy & Environmental Engineering - www.rgpvnotes.in.pdf

Program : B.Tech Subject Name: Energy & Environmental Engineering Subject Code: ES-301 Semester: 3rd Downloaded from be.rgpvnotes.in Unit 1 Introduction to Energy Science: Introduction to energy systems and resources; Introduction to Energy, sustainability & th...

Program : B.Tech Subject Name: Energy & Environmental Engineering Subject Code: ES-301 Semester: 3rd Downloaded from be.rgpvnotes.in Unit 1 Introduction to Energy Science: Introduction to energy systems and resources; Introduction to Energy, sustainability & the environment; Overview of energy systems, sources, transformations, efficiency, and storage; Fossil fuels (coal, oil, oil-bearing shale and sands, coal gasification) - past, present & future, Remedies & alternatives for fossil fuels - biomass, wind, solar, nuclear, wave, tidal and hydrogen; Sustainability and environmental trade-offs of different energy systems; possibilities for energy storage or regeneration (Ex. Pumped storage hydro power projects, superconductor-based energy storages, high efficiency batteries) Energy Energy is the capacity to do work and is required for life processes. An energy resource is something that can produce heat, power life, move objects, or produce electricity. Matter that stores energy is called a fuel. Human energy consumption has grown steadily throughout human history. Early humans had modest energy requirements, mostly food and fuel for fires to cook and keep warm. In today's society, humans consume as much as 110 times as much energy per person as early humans. Most of the energy we use today comes from fossil fuels (stored solar energy). But fossils fuels have a disadvantage in that they are non-renewable on a human time scale, and because other potentially harmful effects on the environment. In any event, the exploitation of all energy sources (with the possible exception of direct solar energy used for heating), ultimately rely on materials on planet Earth. Sustainability & The Environment The defi itio of sustai a ilit is the stud of ho atu al s ste s fu tio , e ai di e se and produce everything it needs for the ecology to remain in balance. It also acknowledges that human civilization takes resources to sustain our modern way of life. The Three Pillars of Sustainability. Economic Development This is the issue that proves the most problematic as most people disagree on political ideology what is and is not economically sound, and how it will affect businesses and by extension, jobs and employability. It is also about providing incentives for businesses and other organizations to adhere to sustainability guidelines beyond their normal legislative requirements. Also, to encourage and foster incentives for the average person to do their bit where and when they can; one person can rarely achieve much, but taken as a group, effects in some areas are cumulative. The supply and demand market is consumerist in nature and modern life requires a lot of resources every single day; for the sake of the environment, getting what we consume under control is the paramount issue. Economic development is about giving people what they want without compromising quality of life, especially in the de elopi g o ld, a d edu i g the fi a ial u de a d ed tape of doi g the ight thi g. Social Development There are many facets to this pillar. Most importantly is awareness of and legislation protection of the health of people from pollution and other harmful activities of business and other organizations. In North America, Europe and the rest of the developed world, there are strong checks and programmers of legislation in place to ensure that people's health and wellness is strongly protected. It is also about maintaining access to basic resources without Page no: 1 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in compromising the quality of life. The biggest hot topic for many people right now is sustainable housing and how we can better build the homes we live in from sustainable material. The final element is education - encouraging people to participate in environmental sustainability and teaching them about the effects of environmental protection as well as warning of the dangers if we cannot achieve our goals. Environmental Protection We all know what we need to do to protect the environment, whether that is recycling, reducing our power consumption by switching electronic devices off rather than using standby, by walking short journeys instead of taking the bus. Businesses are regulated to prevent pollution and to keep their own carbon emissions low. There are incentives to installing renewable power sources in our homes and businesses. Environmental protection is the third pillar and to many, the primary concern of the future of humanity. It defines how we should study and protect ecosystems, air quality, integrity and sustainability of our resources and focusing on the elements that place stress on the environment. Primary Goals of Sustainability The end of poverty and hunger Better standards of education and healthcare - particularly as it pertains to water quality and better sanitation To achieve gender equality Sustainable economic growth while promoting jobs and stronger economies All of the above and more while tackling the effects of climate change, pollution and other environmental factors that can harm and do harm people's health, livelihoods and lives. Sustainability to include health of the land, air and sea Energy Sources There are 5 fundamental sources of energy: 1. Nuclear fusion in the Sun (solar energy) 2. Gravity generated by the Earth & Moon. 3. Nuclear fission reactions. 4. Energy in the interior of the Earth. 5. Energy stored in chemical bonds. Other than this it can be classified in two broad terms:- 1. Renewable resources a. Solar energy b. Wind energy c. Geothermal energy d. Hydropower energy e. Biomass f. Hydrogen and fuel cells 2. Non renewable Resources a. Nuclear energy b. Fuel energy (Coal/ Petroleum) 1. Renewable resources-: A renewable resource is a resource which can be used repeatedly and replaced naturally. Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable (naturally Page no: 2 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in replenished). In 2008, about 19% of global final energy consumption came from renewable, with 13% coming from traditional biomass, which is mainly used for heating, and 3.2% from hydroelectricity. New renewable (small hydro, modern biomass, wind, solar, geothermal, and bio-fuels) accounted for another 2.7% and are growing very rapidly. The share of renewable in electricity generation is around 18%, with 15% of global electricity coming from hydroelectricity and 3% from new renewable. Types of Renewable resources 1. Solar. This form of energy relies on the nuclear fusion power from the core of the Sun. This energy can be collected and converted in a few different ways. The range is from solar water heating with solar collectors or attic cooling with solar attic fans for domestic use to the complex technologies of direct conversion of sunlight to electrical energy using mirrors and boilers or photovoltaic cells. Unfortunately these are currently insufficient to fully power our modern society. 2. Wind The movement of the atmosphere is driven by differences of temperature at the Earth's surface due to varying temperatures of the Earth's surface when lit by sunlight. Wind energy can be used to pump water or generate electricity, but requires extensive areal coverage to produce significant amounts of energy. 3. Hydroelectric energy this form uses the gravitational potential of elevated water that was lifted from the oceans by sunlight. It is not strictly speaking renewable since all reservoirs eventually fill up and require very expensive excavation to become useful again. At this time, most of the available locations for hydroelectric dams are already used in the developed world. 4. Biomass is the term for energy from plants. Energy in this form is very commonly used throughout the world. Unfortunately the most popular is the burning of trees for cooking and warmth. This process releases copious amounts of carbon dioxide gases into the atmosphere and is a major contributor to unhealthy air in many areas. Some of the more modern forms of biomass energy are methane generation and production of alcohol for automobile fuel and fueling electric power plants. 5. Hydrogen and fuel cells these are also not strictly renewable energy resources but are very abundant in availability and are very low in pollution when utilized. Hydrogen can be burned as a fuel, typically in a vehicle, with only water as the combustion product. This clean burning fuel can mean a significant reduction of pollution in cities. Or the hydrogen can be used in fuel cells, which are similar to batteries, to power an electric motor. In either case significant production of hydrogen requires abundant power. Due to the need for energy to produce the initial hydrogen gas, the result is the relocation of pollution from the cities to the power plants. There are several promising methods to produce hydrogen, such as solar power, that may alter this picture drastically. 6. Geothermal power Energy left over from the original accretion of the planet and augmented by heat from radioactive decay seeps out slowly everywhere, everyday. In certain areas the geothermal gradient (increase Page no: 3 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in in temperature with depth) is high enough to exploit to generate electricity. This possibility is limited to a few locations on Earth and many technical problems exist that limit its utility. Another form of geothermal energy is Earth energy, a result of the heat storage in the Earth's surface. Soil everywhere tends to stay at a relatively constant temperature, the yearly average, and can be used with heat pumps toheat a building in winter and cool a building in summer. This form of energy can lessen the need for other power to maintain comfortable temperatures in buildings, but cannot be used to produce electricity. 2. Non renewable Resources 1. Nuclear Fission Reactions Radioactive Uranium is concentrated and made into fuel rods that generate large amounts of heat as a result of radioactive decay. This heat is used to turn water into steam. Expansion of the steam can then be used to drive a turbine and generate electricity. Once proposed as a cheap, clean, and safe way to generate energy, Nuclear power has come under some disfavor. Costs of making sure nuclear power plants are clean and safe and the problem of disposing of radioactive wastes, which are unsafe, as well as questions about the safety of the plants under human care, has contributed to this disfavor. 2. Energy in the Interior of the Earth Decay of radioactive elements has produced heat throughout Earth history. It is this heat that causes the temperature to increase with depth in the Earth and is responsible for melting of mantle rocks to form magmas. Magmas can carry the heat upward into the crust. Groundwater circulating in the vicinity of igneous intrusions carries the heat back toward the surface. If this hot water can be tapped, it can be used directly to heat homes, or if trapped at great depth under pressure it can be turned into steam which will expand. 3. Fossil Fuels The origin of fossil fuels and biomass energy in general, starts with photosynthesis. Photosynthesis is the most important chemical reaction to us as human beings, because without it, we could not exist. Photosynthesis is the reaction that combines water and carbon dioxide from the Earth and its atmosphere with solar energy to form organicmolecules that make up plants and oxygen essential for respiration. Because all life forms depend on plants for nourishment, either directly or indirectly, photosynthesis is the basis for life on Earth.Thus when oxygen is added to organic material, either through decay by reaction with oxygen in the atmosphere, or by adding oxygen directly by burning, energy is produced, and water and carbon dioxide return to the Earth or its atmosphere. 4. Petroleum To produce a fossil fuel, the organic matter must be rapidly buried in the Earth so that it does not oxidize (react with oxygen in the atmosphere). Then a series of slow chemical reactions occur which turn the organic molecules into hydrocarbons- Oil and Natural Gas, together called Petroleum. Hydrocarbons are complex organic molecules that consist of chains of hydrogen and carbon. Energy transformation Energy transformation also termed as energy conversion, is the process of changing energy from one of its forms into another. In physics, energy is a quantity that provides the capacity Page no: 4 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in to perform many actions—think of lifting or warming an object. In addition to being convertible, energy is transferable to a different location or object, but it cannot be created or destroyed. Energy in many of its forms may be used in natural processes, or to provide some service to society such as heating, refrigeration, lightening or performing mechanical work to operate machines. For example, in order to heat your home, your furnace can burn fuel, whose chemical potential energy is thus converted into thermal energy, which is then transferred to your home's air in order to raise its temperature. Conversion of thermal energy to other types:- Conversions to thermal energy (thus raising the temperature) from other forms of energy, may occur with essentially 100% efficiency[citation needed] (many types %, such as when potential energy is converted to kinetic energy as an object falls in vacuum, or when an object orbits nearer or farther from another object, in space. Though, conversion of thermal energy to other forms, thus reducing the temperature of a system, has strict limitations, often keeping its efficiency much less than 100% (even when energy is not allowed to escape from the system). This is because thermal energy has already been partly spread out among many available states of a collection of microscopic particles constituting the system, which can have enormous numbers of possible combinations of momentum and position (these combinations are said to form a phase space). In such circumstances, a measure called entropy, or evening-out of energy distributions, dictates that future states of an isolated system must be of at least equal evenness in energy distribution. In other words, there is no way to concentrate energy without spreading out energy somewhere else. Transformation of kinetic energy of charged particles to electric energy:- In order to make the energy transformation more efficient, it is desirable to avoid the thermal conversion. For example, the efficiency of nuclear energy reactors, where kinetic energy of nuclei is first converted to thermal energy and then to electric energy, lies around 35%.By direct conversion of kinetic energy to electric, i.e. by eliminating the thermal energy transformation, the efficiency of energy transformation process can be dramatically improved. Energy Transformation From The Early Universe Energy transformations in the universe over time are (generally) characterized by various kinds of energy which has been available since the Big Bang, later being "released" (that is, transformed to more active types of energy such as kinetic or radiant energy), when a  Release of energy from gravitational potential triggering mechanism is available to do it.  Release of energy from radioactive potential  Release of energy from hydrogen fusion potential  For instance, a coal-fired power plant involves these energy transformations: Examples of sets of energy conversions in machines  Chemical energy in the coal converted to thermal energy in the exhaust gases of combustion. Page no: 5 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in  Thermal energy of the exhaust gases converted into thermal energy of steam through  the heat exchanger.  Thermal energy of steam converted to mechanical energy in the turbine. Mechanical energy of the turbine converted to electrical energy by the generator,  which is the ultimate output In such a system, the first and fourth step are highly efficient, but the second and third steps are less efficient. The most efficient gas-fired electrical power stations can achieve 50% conversion efficiency. Oil- and coal-fired stations achieve less. In a conventional automobile, these energy transformations are involved:  Chemical energy in the fuel converted to kinetic energy of expanding gas via  combustion  Kinetic energy of expanding gas converted to linear piston movement  Linear piston movement converted to rotary crankshaft movement  Rotary crankshaft movement passed into transmission assembly  Rotary movement passed out of transmission assembly  Rotary movement passed through differential  Rotary movement passed out of differential to drive wheels Rotary movement of drive wheels converted to linear motion of the vehicle. Energy storage Energy storage is the capture of energy produced at one time for use at a later time. A device that stores energy is sometimes called an accumulator or battery. Energy comes in multiple forms including radiation, chemical, gravitational potential, electrical potential, electricity, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms. Bulk energy storage is currently dominated by hydroelectric dams, both conventional as well as pumped. Some technologies provide short-term energy storage, while others can endure for much longer. A wind-up clock stores potential energy (in this case mechanical, in the spring tension), a rechargeable battery stores readily convertible chemical energy to operate a mobile phone, and a hydroelectric dam stores energy in a reservoir as gravitational potential energy. Fossil fuels such as coal and gasoline store ancient energy derived from sunlight by organisms that later died, became buried and over time were then converted into these fuels. Food (which is made by the same process as fossil fuels) is a form of energy stored in chemical form. Ice storage tanks store ice frozen by cheaper energy at night to meet peak daytime demand for cooling. The energy isn't stored directly, but the work-product of consuming energy (pumping away heat) is stored, having the equivalent effect on daytime consumption. Fossile fuel:- a fossil fuel is a fuel formed by natural processes, such as anaerobic decomposition of buried dead organisms, containing energy originating in ancient photosynthesis. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years. Fossil fuels contain high percentages of carbon and include petroleum, coal, Page no: 6 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in and natural gas. Other commonly used derivatives include kerosene and propane. Fossil fuels range from volatile materials with low carbon to hydrogen ratios like methane, to liquids like petroleum, to non-volatile materials composed of almost pure carbon, like anthracite coal. Methane can be found in hydrocarbon fields either alone, associated with oil, or in the form of methane catharses. Advantages of Fossil Fuels  A major advantage of fossil fuels is their capacity to generate huge amounts of electricity in just a single location.  Fossil fuels are very easy to find.  When coal is used in power plants, they are very cost effective. Coal is also in abundant supply.  Transporting oil and gas to the power stations can be made through the use of pipes making it an easy task.  Power plants that utilize gas are very efficient.  Power stations that make use of fossil fuel can be constructed in almost any location. This is possible as long as large quantities of fuel can be easily brought to the power plants. Disadvantages of Fossil Fuels  Pollution is a major disadvantage of fossil fuels. This is because they give off carbon dioxide when burned thereby causing a greenhouse effect. This is also the main contributory factor to the global warming experienced by the earth today.  Coal also produces carbon dioxide when burned compared to burning oil or gas. Additionally, it gives off sulphur dioxide, a kind of gas that creates acid rain.  Environmentally, the mining of coal results in the destruction of wide areas of land. Mining this fossil fuel is also difficult and may endanger the lives of miners. Coal mining is considered one of the most dangerous jobs in the world.  Power stations that utilize coal need large amounts of fuel. In other words, they not only need truckloads but trainloads of coal on a regular basis to continue operating and generating electricity. This only means that coal-fired power plants should have reserves of coal in a large area near the plants location.  Use of natural gas can cause unpleasant odors and some problems especially with transportation.  Use of crude oil causes pollution and poses environmental hazards such as oil spills when oil tankers, for instance, experience leaks or drown deep under the sea. Crude oil contains toxic chemicals which cause air pollutants when combusted. Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon, along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is a fossil fuel that forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, after that bituminous coal, and lastly anthracite. This involves biological and geological processes. The geological processes take place over millions of years. Formation Page no: 7 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in Example chemical structure of coal At various times in the geologic past, the Earth had dense forests in low-lying wetland areas. Due to natural processes such as flooding, these forests were buried underneath soil. As more and more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. As the process continued the plant matter was protected from biodegradation and oxidation, usually by mud or acidic water. This trapped the carbon in immense peat bogs that were eventually covered and deeply buried by sediments. Under high pressure and high temperature, dead vegetation was slowly converted to coal. As coal contains mainly carbon, the conversion of dead vegetation into coal is called carbonization Production of electricity from coal Steam coal, also known as thermal coal, is used in power stations to generate electricity. Coal is first milled to a fine powder, which increases the surface area and allows it to burn more quickly. In these pulverised coal combustion (PCC) systems, the powdered coal is blown into the combustion chamber of a boiler where it is burnt at high temperature (see diagram). The hot gases and heat energy produced converts water – in tubes lining the boiler – into steam. The high pressure steam is passed into a turbine containing thousands of propeller-like blades. The steam pushes these blades causing the turbine shaft to rotate at high speed. A generator is mounted at one end of the turbine shaft and consists of carefully wound wire coils. Electricity is generated when these are rapidly rotated in a strong magnetic field. After passing through the turbine, the steam is condensed and returned to the boiler to be heated once again. The electricity generated is transformed into the higher voltages (up to 400,000 volts) used for economic, efficient transmission via power line grids. When it nears the point of consumption, such as our homes, the electricity is transformed down to the safer 100-250 voltage systems used in the domestic market. Page no: 8 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in Efficiency improvements Improvements continue to be made in conventional PCC power station design and new combustion technologies are being developed. These allow more electricity to be produced from less coal - known as improving the thermal efficiency of the power station. Efficiency gains in electricity generation from coal-fired power stations will play a crucial part in reducing CO2 emissions at a global level. A one percentage point improvement in the efficiency of a conventional pulverised coal combustion plant results in a 2-3% reduction in CO2 emissions. Shale oil Shale oil is unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas. The resulting oil can be used immediately as a fuel or upgraded to meet refinery feedstock specifications by adding hydrogen and removing impurities such as sulfur and nitrogen. The refined products can be used for the same purposes as those derived from crude oil. The term "shale oil" is also used fo ude oil p odu ed f o shale s of othe e lo permeability formations. However, to reduce the risk of confusion of shale oil produced from oil shale with crude oil in oil- ea i g shale s, the te "tight oil" is p efe ed fo the latte. Shale oil extraction Shale oil is extracted by pyrolysis, hydrogenation, or thermal dissolution of oil shale. The pyrolysis of the rock is performed in a retort, situated either above ground or within the rock formation itself. As of 2008, most oil shale industries perform the shale oil extraction process after the rock is mined, crushed and transported to a retorting facility, although several experimental technologies perform the process in place (in-situ). The temperature at which the kerogen decomposes into usable hydrocarbons varies with the time-scale of the process; in the above-ground retorting process decomposition begins at 300 °C (570 °F), but proceeds Page no: 9 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in more rapidly and completely at higher temperatures. Decomposition takes place most quickly at a temperature between 480 and 520 °C (900 and 970 °F). Hydrogenation and thermal dissolution (reactive fluid processes) extract the oil using hydrogen donors, solvents, or a combination of these. Thermal dissolution involves the application of solvents at elevated temperatures and pressures, increasing oil output by cracking the dissolved organic matter. Different methods produce shale oil with different properties. Properties of Shale Properties of raw shale oil vary depending on the composition of the parent oil shale and the extraction technology used. Like conventional oil, shale oil is a complex mixture of hydrocarbons, and it is characterized using bulk properties of the oil. Shale oil usually contains large quantities of olefinic and aromatic hydrocarbons. Shale oil can also contain significant quantities of heteroatoms. A typical shale oil composition includes 0.5–1% of oxygen, 1.5–2% of nitrogen and 0.15–1% of sulfur, and some deposits contain more heteroatoms. Mineral particles and metals are often present as well. Generally, the oil is less fluid than crude oil, becoming pourable at temperatures between 24 and 27 °C (75 and 81 °F), hile o e tio al ude oil is pou a le at te pe atu es et ee − to °C − to °F); this property affects shale oil's ability to be transported in existing pipelines Coal Gasification Coal gasification is the process of producing syngas–a mixture consisting primarily of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), methane (CH4), and water vapour (H2O)– from coal and water, air and/or oxygen. coal was gasified using early technology to produce coal gas (also known as "town gas"), which is a combustible gas traditionally used for municipal lighting and heating before the advent of industrial-scale production of natural gas. In current practice, large-scale instances of coal gasification are primarily for electricity generation, such as in integrated gasification combined cycle power plants, for production of chemical feedstocks, or for production of synthetic natural gas. The hydrogen obtained from coal gasification can be used for various purposes such as making ammonia, powering a hydrogen economy, or upgrading fossil fuels. Page no: 10 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in During gasification, the coal is blown through with oxygen and steam (water vapor) while also being heated (and in some cases pressurized). If the coal is heated by external heat sources the process is called "allothermal", while "autothermal" process assumes heating of the coal via exothermal chemical reactions occurring inside the gasifier itself. It is essential that the oxidizer supplied is insufficient for complete oxidizing (combustion) of the fuel. During the reactions mentioned, oxygen and water molecules oxidize the coal and produce a gaseous mixture of carbon dioxide (CO2), carbon monoxide (CO), water vapour (H2O), and molecular hydrogen (H2). (Some by-products like tar, phenols, etc. are also possible end products, depending on the specific gasification technology utilized.) This process has been conducted in-situ within natural coal seams (referred to as underground coal gasification) and in coal refineries. The desired end product is usually syngas (i.e., a combination of H 2 + CO), but the produced coal gas may also be further refined to produce additional quantities of H2: 3C (i.e., coal) + O2 + H2O → H2 + 3CO If the refiner wants to produce alkanes (i.e., hydrocarbons present in natural gas, gasoline, and diesel fuel), the coal gas is collected at this state and routed to a Fischer-Tropsch reactor. If, however, hydrogen is the desired end-product, the coal gas (primarily the CO product) undergoes the water gas shift reaction where more hydrogen is produced by additional reaction with water vapor: CO + H2O → CO2 + H2 Although other technologies for coal gasification currently exist, all employ, in general, the same chemical processes. For low-grade coals (i.e., "brown coals") which contain significant amounts of water, there are technologies in which no steam is required during the reaction, with coal (carbon) and oxygen being the only reactants. As well, some coal gasification technologies do not require high pressures. Some utilize pulverized coal as fuel while others work with relatively large fractions of coal. Gasification technologies also vary in the way the blowing is supplied. "Direct blowing" assumes the coal and the oxidizer being supplied towards each other from the opposite sides of the reactor channel. In this case the oxidizer passes through coke and (more likely) ashes to the reaction zone where it interacts with coal. The hot gas produced then passes fresh fuel and heats it while absorbing some products of thermal destruction of the fuel, such as tars and phenols. Thus, the gas requires significant refining before being used in the Fischer-Tropsch reaction. Products of the refinement are highly toxic and require special facilities for their utilization. As a result, the plant utilizing the described technologies has to be very large to be economically efficient. One of such plants called SASOL is situated in the Republic of South Africa (RSA). It was built due to embargo applied to the country preventing it from importing oil and natural gas. RSA is rich in Bituminous coal and Anthracite and was able to arrange the use of the well known high pressure "Lurgi" gasification process developed in Germany in the first half of 20th century. "Reversed blowing" (as compared to the previous type described which was invented first) assumes the coal and the oxidizer being supplied from the same side of the reactor. In this case there is no chemical interaction between coal and oxidizer before the reaction zone. The gas produced in the reaction zone passes solid products of gasification (coke and ashes), and CO2 and H2O contained in the gas are additionally chemically restored to CO and H2. As compared to the "direct blowing" technology, no toxic by-products are present in the gas: those are disabled in the reaction zone. Underground coal gasification Page no: 11 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in Underground coal gasification is an industrial gasification process, which is carried out in non- mined coal seams using injection of a gaseous oxidizing agent, usually oxygen or air, and bringing the resulting product gas to surface through production wells drilled from the surface. The product gas could to be used as a chemical feedstock or as fuel for power generation. The technique can be applied to resources that are otherwise not economical to extract and also offers an alternative to conventional coal mining methods for some resources. Compared to traditional coal mining and gasification, UCG has less environmental and social impact, though some concerns including potential for aquifer contamination are known Carbon capture technology Carbon capture, utilization, and sequestration (or storage) is increasingly being utilized in modern coal gasification projects to address the greenhouse gas emissions concern associated with the use of coal and carbonaceous fuels. In this respect, gasification has a significant advantage over conventional coal combustion, in which CO 2 resulting from combustion is considerably diluted by nitrogen and residual oxygen in the near-ambient pressure combustion exhaust, making it relatively difficult, energy-intensive, and expensive to capture the CO2 this is k o as post- o ustio CO2 capture). CO2 capture technology options All coal gasification-based conversion processes require removal of hydrogen sulfide (H 2S; an acid gas) from the syngas as part of the overall plant configuration. Typical acid gas removal (AGR) processes employed for gasification design are either a chemical solvent system (e.g., amine gas treating systems based on MDEA, for example) or a physical solvent system (e.g., Rectisol or Selexol). Process selection is mostly dependent on the syngas cleanup requirement and costs. Conventional chemical/physical AGR processes using MDEA, Rectisol or Selexol are commercially proven technologies and can be designed for selective removal of CO2 in addition to H2S from a syngas stream. For significant capture of CO 2 from a gasification plant (e.g., > 80%) the CO in the syngas must first be converted to CO 2 and hydrogen (H2) via a water-gas-shift (WGS) step upstream of the AGR plant. For gasification applications, or IGCC, the plant modifications required to add the ability to capture CO2 are minimal. The syngas produced by the gasifiers needs to be treated through various processes for the removal of impurities already in the gas stream, so all that is required to remove CO2 is to add the necessary equipment, an absorber and regenerator, to this process train. In combustion applications, smodifications must be done to the exhaust stack and because of the lower concentrations of CO2 present in the exhaust, much larger volumes of total gas require processing, necessitating larger and more expensive equipment. By-products he by-products of coal gas manufacture included coke, coal tar, sulfur and ammonia; all useful products. Dyes, medicines, including sulfa drugs, saccharin and many organic compounds are therefore derived from coal gas. Coke is used as a smokeless fuel and for the manufacture of water gas and producer gas. Coal tar is subjected to fractional distillation to recover various products, including tar, for roads  benzole, a motor fuel  creosote, a wood preservative Page no: 12 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in  phenol, used in the manufacture of plastics  cresols, disinfectants Sulfur is used in the manufacture of sulfuric acid and ammonia is used in the manufacture of fertilisers. Indian Scenario India is one of the countries where the present level of energy consumption, by world standards, is very low. The estimate of annual energy consumption in India is about 330 Million Tones Oil Equivalent (MTOE) for the year 2004. Accordingly, the per capita consumption of energy is about 305 Kilogram Oil Equivalent (KGOE). As compared to this, the energy consumption in some of the other countries is of the order of over 4050 for Japan, over 4275 for South Korea, about 1200 for China, about 7850 for USA, about 4670 for OECD countries and the world average is about 1690. In so far as electricity consumption is concerned, India has reached a level of about 600-kilowatt hour (kwh) per head per year. The comparable figures for Japan are about 7,800, for South Korea about 7,000, for China about 1380, for USA about 13,000, for OECD countries about 8050 and world average are about 2430. Thus, both in terms of per capita energy consumption and in terms of per capita electricity consumption, India is far behind many countries, and as a matter of fact, behind even the world average. Therefore, to improve the standards of living of Indian people and to let them enjoy the benefit of economic development, it is imperative that both energy consumption and electricity consumption level is enhanced. India is targeting a growth rate of 9 – 10%, having already reached a level of almost 8%. To sustain the double-digit growth rate for next 10-15 years, it would be essential that the level of energy availability and consumption, and electricity consumption in particular, is enhanced substantially.In the profile of energy sources in I dia, oal has a do i a t positio. Coal o stitutes a out % of I dia s p i a e e g resources followed by Oil (36%), Natural Gas (9%), Nuclear (2%) and Hydro (2%). To address the issue concerning energy consumption, and more particularly, the need for enhancing the energy supply, India has accorded appropriate priority to both - supply side management and demand side management. Non-Conventional Energy Sources Indian Government has accorded very high priority to develop and expand installed capacity base through non-conventional sources of electricity generation. There is a separate Ministry in the Government of India to exclusively focus on this important area of power generation. National Electricity Policy notified in 2005 in pursuance of the Electricity Act, 2003, prescribes that State Electricity Regulatory Commissions should prescribe a proportion of power which should be produced and supplied to the grid through the non-conventional sources. Some of the Regulatory Commissions have come out with specific policy guidelines with a different approach on tariff for these plants in order to encourage these technologies and plants. National Electricity Tariff Policy mandates that State Commissions should fix such minimum percentage latest by April, 2006. India has very high potential for these capacities: Page no: 13 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in It may be seen from the above that India has achieved substantial success on wind turbine based power generation. Ministry of Non-conventional Energy Sources (MNES) has set a target of achieving at least 10,000 MW capacity through various non-conventional sources, by the year 2012. Conventional Sources of Electricity Generation Fossil fuel based thermal power, hydro-electric, and nuclear constitute the conventional sources of power. Non-conventional sources are less than 5% of total installed capacity in India. The present installed capacity (as in March 2006) is about 1,25,000 MW, consisting of coal based plants (56%), gas based plants (10%), hydro- electric (26%), nuclear (3%) non-conventional (5%). Indian Power Sector was opened up for private power generation in 1991. In terms of ownership structure, the profile consists of Central Government owned companies (32%), State Government owned companies/Electricity Boards (57%) and Private Sector (11%). 100% FDI is permitted in all segments of electricity industry – viz. Generation, Transmission, Distribution, Trading. In the last three years far-reaching structural changes have been introduced in the Indian Electricity Sector. Electricity Act 2003 is an historic legislative initiative with powerful potential to transform the power sector industry and market structure. Most important features of the Electricity Act 2003 are as follows: 1. The Act creates a liberal and transparent framework for power development 2. It facilitates investment by creating competitive environment and reforming distribution segment of power industry. 3. Entry Barriers have been removed/reduced in following areas: a) Delicensed generation. b) Freedom to captive generation including group captive c) Recognizing trading as an independent activity d) Open access in transmission facilitating multi buyer and seller model. 4. Open access to consumers above 1 MW within five years commencing from 27 th January, 2004 (date of enforcement of amendment to Electricity Act) Regulators have been mandated to ensure this. 5. Multiple licenses in distribution in the same area of supply so that competition could yield better services to consumers. 6. Regulatory Commissions – to develop market and to fix tariff. Biomass Energy Renewable energy from plants and animals/ biomass is a renewable energy source from living or recently living plant and animal materials which can be used as fuel. An example of biomass is plant material that produces electricity with steam. An example of biomass is animal fossil fuel. Biomass is organic material that comes from plants and animals, and it is a renewable source of energy. Biomass contains stored energy from the sun. Plants absorb the sun's energy in a process called photosynthesis. When biomass is burned, the chemical energy in biomass is released as heat. Biomass can be burned directly or converted to liquid biofuels or biogas that can be burned as fuels. Or Biomass energy is the energy which is contained inside plants and animals. This can include organic matter of all kinds: plants, animals, or waste products from organic sources. These sorts of energy sources are known as biofuels and typically include wood chips, rotted trees, Page no: 14 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in manure, sewage, mulch, and tree components. Chlorophyll present in plants absorbs carbon dioxide from the atmosphere and water from the ground through the process of photosynthesis. The same energy is passed to animals when they eat them. It is considered to be as renewable source of energy because carbon dioxide and water contained inside plants and animals are released back in to the atmosphere when they are burned and we can grow more plants and crops to create biomass energy. Types of Biomass We use four types of biomass today: 1) wood and agricultural products; 2) solid waste; 3) landfill gas; and 4) alcohol fuels. 1. Wood and Agricultural Biomass:- Most biomass used today is home grown energy. Wood-logs, chips, bark, and sawdust-accounts for about 79 percent of biomass energy. But any organic matter can produce biomass energy. Other biomass sources include agricultural waste products like fruit pits and corn cobs. 2. Solid Waste:- There is nothing new about people burning trash. What's new is burning trash to generate electricity. This turns waste into a usable form of energy. A ton (2,000 pounds) of garbage contains about as much heat energy, as pounds of coal. Power plants that burn garbage for energy are called waste- to-energy plants. These plants generate electricity much as coal-fired plants do except that garbage-not coal-is the fuel used to fire an industrial boiler. Making electricity from garbage costs more than making it from coal and other energy sources. The main advantage of burning solid waste is it reduces the amount of garbage dumped in landfills by 60 to 90 percent, and reduces the cost of landfill disposal. 3. Landfill Gas:- Bacteria and fungi are not picky eaters. They eat dead plants and animals, causing them to rot or decay. Even though this natural process is slowed in the artificial environment of a landfill, a substance called methane gas is still produced as the waste decays. New regulations require landfills to collect methane gas for safety and environmental reasons. Methane gas is colorless and odorless, but it is not harmless. The gas can cause fires or explosions if it seeps into nearby homes and is ignited. Landfills can collect the methane gas, purify it, and then use it as an energy source. Methane, which is the same thing as natural gas, is a good energy source. Most gas furnaces and Page no: 15 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in gas stoves use methane supplied by natural gas utility companies. The city landfill in Florence, Alabama recovers 32 million cubic feet of methane gas a day. The city purifies the gas and then pumps it into natural gas pipelines. 4. Alcohol Fuels:- Wheat, corn, and other crops can be converted into a variety of liquid fuels including ethanol and methanol. Using ethanol as a motor fuel is nothing new. Its use is almost as old as the automobile. Gasohol does have some advantages over gasoline. It has a higher octane rating than gasoline (provides your car with more power), and it is cleaner-burning than unleaded gasoline, with one-third less carbon monoxide emissions. Gasohol may also help reduce America's dependence on foreign oil. Sources of Biomass Here are various biomass sources, which are a great source of energy that can be used for various applications: 1) Wood and waste wood: Wood is the most commonly used type of biomass. Since the earliest days the fuel being used for cooking and heating is the wood. Even at present wood as the biomass material is major source of energy in a number of developing countries. Wood as a biomass can be used in various forms like large wooden blocks obtained from the trees, wooden chips, and saw dust. The wasted wood and wooden scrap are also the source of biomass. 2) Leaves of the plants: In the densely planted places lots of leaves fall from the trees. These can be dried, powdered and converted into small pieces, which can be used as the biomass fuel to generate heat used usually for cooking food. 3) Broken branches and twigs of the trees: No part of the plant goes wasted when it leaves the main body of the tree. Large and small branches and even all the small twigs are the source of biomass energy. 4) Agricultural waste: Lots of waste materials obtained from the farms are a great source of biomass materials. Livestock waste can also be used to generate methane gas. 5) Waste paper: Tons of waste paper is produced every day. These can be burnt to produce lots of heat. The paper is manufactured from the plants, so it is considered to be biomass material. 6) Garbage: The garbage, also called as municipal solid waste is another source of biomass. The garbage can be in the form of food scrap, lawn clippings, waste paper, fallen leaves etc all mixed together or collected individually. 7) Human waste: The human wastes are also considered to the source of biomass. These can used to generate methane gas which is the major component of natural gas. Biomass Gasification Biomass gasification, or producing gas from biomass, involves burning biomass under restricted air supply for the generation of producer gas. Producer gas is a mixture of gases: Page no: 16 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in 18%–22% carbon monoxide (CO), 8%–12% hydrogen (H2), 8%–12% carbon dioxide (CO2), 2%– 4% methane (CH4) and 45%–50% nitrogen (N2) making up the rest. Gasification reactions Producing gas from biomass consists of the following main reactions, which occur inside a biomass gasifier. 1. Drying: Biomass fuels usually contain 10%–35% moisture. When biomass is heated to about 100 °C, the moisture is converted into steam. 2. Pyrolysis: After drying, as heating continues, the biomass undergoes pyrolysis. Pyrolysis involves burning biomass completely without supplying any oxygen. As a result, the biomass is decomposed or separated into solids, liquids, and gases. Charcoal is the solid part, tar is the liquid part, and flue gases make up the gaseous part. 3. Oxidation: Air is introduced into the gasifier after the decomposition process. During oxidation, which takes place at about 700–1,400 °C, charcoal, or the solid carbonized fuel, reacts with the oxygen in the air to produce carbon dioxide and heat. C + O → CO + heat 4. Reduction: At higher temperatures and under reducing conditions, that is when not enough oxygen is available, the following reactions take place forming carbon dioxide, hydrogen, and methane. C + CO → CO C + H O → CO + H CO + H O → CO + H C + H → CH Types of gasifiers Gasifiers can be classified based on the density factor, which is a ratio of the solid matter (the dense phase) a gasifier can burn to the total volume available. Gasifiers can be (a) dense phase reactors, or (b) lean phase reactors. Dense phase reactors In dense phase reactors, the feedstock fills most of the space in the reactor. They are common, available in different designs depending upon the operating conditions, and are of three types: downdraft, updraft, and cross-draft. 1. Downdraft or co-current gasifiers:- The downdraft (also known as co-current) gasifier is the most common type of gasifier. In downdraft gasifiers, the pyrolysis zone is above the combustion zone and the reduction zone is below the combustion zone. Fuel is fed from the top. The flow of air and gas is downwards (hence the name) through the combustion and reduction zones. The term co-current is used because air moves in the same direction as that of fuel, downwards. A downdraft gasifier is so designed that tar, which is produced in the pyrolysis zone, travels through the combustion zone, where it is broken down or burnt. As a result, the mixture of gases in the exit stream is relatively clean. The position of the combustion zone is thus a critical element in the downdraft gasifier, its main advantage being that it produces gas with low tar content, which is suitable for gas engines. Page no: 17 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in Updraft or counter-current gasifier In updraft gasifiers (also known as counter-current), air enters from below the grate and flows upwards, whereas the fuel flows downwards. An updraft gasifier has distinctly defined zones for partial combustion, reduction, pyrolysis, and drying. The gas produced in the reduction zone leaves the gasifier reactor together with the products of pyrolysis from the pyrolysis zone and steam from the drying zone. The resulting combustible producer gas is rich in hydrocarbons (tars) and, therefore, has a higher calorific value, which makes updraft gasifiers more suitable where heat is needed, for example in industrial furnaces. The producer gas needs to be thoroughly cleaned if it is to be used for generating electricity. Cross-draft gasifier In a cross-draft gasifier, air enters from one side of the gasifier reactor and leaves from the other. Cross-draft gasifiers have a few distinct advantages such as compact construction and low cleaning requirements. Also, cross-draft gasifiers do not need a grate; the ash falls to the bottom and does not come in the way of normal operation. Page no: 18 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in Lean phase reactors Lean phase gasifiers lack separate zones for different reactions. All reactions – drying, combustion, pyrolysis, and reduction – occur in one large reactor chamber. Lean phase reactors are mostly of two types, fluidized bed gasifiers and entrained-flow gasifiers. Fluidized bed gasifiers In fluidized bed gasifiers, the biomass is brought into an inert bed of fluidized material (e.g. sand, char, etc.). The fuel is fed into the fluidized system either above-bed or directly into the bed, depending upon the size and density of the fuel and how it is affected by the bed velocities. During normal operation, the bed media is maintained at a temperature between 550 °C and 1000 °C. When the fuel is introduced under such temperature conditions, its drying and pyrolyzing reactions proceed rapidly, driving off all gaseous portions of the fuel at relatively low temperatures. The remaining char is oxidized within the bed to provide the heat source for the drying and devolatilizing reactions to continue. Fluidized bed gasifiers are better than dense phase reactors in that they produce more heat in short time due to the abrasion phenomenon between inert bed material and biomass, giving a uniformly high (800–1000 ºC) bed temperature. A fluidized bed gasifier works as a hot bed of sand particles agitated constantly by air. Air is distributed through nozzles located at the bottom of the bed. Entrained-flow gasifiers In entrained-flow gasifiers, fuel and air are introduced from the top of the reactor, and fuel is carried by the air in the reactor. The operating temperatures are 1200–1600 °C and the pressure is 20–80 bar. Entrained-flow gasifiers can be used for any type of fuel so long as it is dry (low moisture) and has low ash content. Due to the short residence time (0.5–4.0 seconds), high temperatures are required for such gasifiers. The advantage of entrained-flow gasifiers is that the gas contains very little tar. Page no: 19 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in The fixed bed The fixed bed gasification system consists of a reactor/gasifier with a gas cooling and cleaning system. The fixed bed gasifier has a bed of solid fuel particles through which the gasifying media and gas move either up or down. It is the simplest type of gasifier consisting of usually a cylindrical space for fuel feeding unit, an ash removal unit and a gas exit. In the fixed bed gasifier, the fuel bed moves slowly down the reactor as the gasification occurs. The fixed bed gasifiers are of simple construction and generally operate with high carbon conversion, long solid residence time, low gas velocity and low ash carry over. In fixed bed gasifiers, tar removal used to be a major problem, however recent progress in thermal and catalytic conversion of tar has given credible options. Comperitive diagram of gasifiers Types Of Conversion Technologies There are four types of conversion technologies currently available, each appropriate for specific biomass? types and resulting in specific energy products: 1. Thermal conversion is the use of heat, with or without the presence of oxygen, to convert biomass materials or feedstocks into other forms of energy. Thermal conversion technolgies include direct combustion, pyrolysis, and torrefaction. Page no: 20 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in As the term implies, thermal conversion involves the use of heat as the primary mechanism for converting biomass into another form. Combustion, pyrolysis, torrefaction, and gasification are the basic thermal conversion technologies either in use today or being developed for the future. 1. Combustion Direct combustion is the burning of biomass in the presence of oxygen. Furnaces and boilers are used typically to produce steam for use in district heating/cooling systems or to drive turbines to produce electricity. In a furnace, biomass burns in a combustion chamber converting the biomass into heat. The heat is distributed in the form of hot air or water. In a boiler, the heat of combustion is converted into steam. Steam can be used to p odu e ele t i it , e ha i al e e g , o heati g a d ooli g. A oile s steam contains 60-85% of the energy in biomass fuel. Co-firing – This is a sub-set of combustion based power production. Some of the modern coal fired power plants use biomass for co-firing along with coal. It is quite efficient, cost-effective and requires moderate additional investment. In general, combustion efficiency of biomass can be 10 percentage points lower than for coal at the same installation, but co-firing efficiency in large-scale coal plants (35%-45%) is higher than the efficiency of biomass-dedicated plants. In the case of co-combustion of up to 5%-10% of biomass (in energy terms) only minor changes in the handling equipment are needed and the boiler is not noticeably de-rated. 2. Pyrolysis These processes do not necessarily produce useful energy directly, but under controlled temperature and oxygen conditions are used to convert biomass feedstocks into gas, oil or forms of charcoal. These energy products are more energy dense than the original biomass, and therefore reduce transport costs, or have more predictable and convenient combustion characteristics allowing them to be used in internal combustion engines and gas turbines. Pyrolysis is a processes of subjecting a biomass feedstock to high temperatures (greater than 430 °C) under pressurized environments and at low oxygen levels. In the process, biomass undergoes partial combustion. Processes of pyrolysis result in liquid fuels and a solid residue called char, or biochar. Biochar is like charcoal and rich in carbon. Liquid phase products result from temperatures which are too low to destroy all of the carbon molecules in the biomass so the result is production of tars, oils, methanol, acetone, etc. The t o ai ethods of p ol sis a e fast p ol sis a d slo p ol sis. Fast pyrolysis yields 60% bio-oil, 20% biochar, and 20% syngas, and can be done in seconds, whereas slow pyrolysis can be optimized to produce substantially more char (~50%) along with organic gases, but takes on the order of hours to complete. In either case, the gas or oil can be used as a fuel for firing the boiler for steam production and subsequent power production. Typically pyrolysis plants work well beyond 2 MW scale, while gasification plants work well until 2 MW scale, at the current technological progress. Thus, it can be said that pyrolysis takes off where gasification ends. Slow Pyrolysis In the case of slow pyrolysis when you get an organic gas and charcoal. The gas can be cooled and fed to a gas engine for power production. Cooling this gas however results in a significant amount of hydrocarbons being removed. Thus most of the energy is wasted away. A more efficient idea that is being explored is to use this heterogeneous gas straight for combustion of boilers and running a steam cycle. Charcoal is a valuable product, which fetches anywhere between Rs 10-Rs 25 per Kg. It Page no: 21 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in has a much better calorific value than coal and people in many places use charcoal because coal might not be available in those places. Fast Pyrolysis Fast pyrolysis is a process in which organic materials are rapidly heated to 450 - 600°C in absence of air. Under these conditions, organic vapors, permanent gases and charcoal are produced. The vapors are condensed to pyrolysis oil. Typically, 50 - 75 wt % of the feedstock is converted into pyrolysis oil. The pyrolysis oil can be used as a replacement for furnace oil. 3. Torrefaction:- Like pyrolysis, is the conversion of biomass with the application of heat in the absence of oxygen, but at lower temperatures than those typically used in pyrolysis. In torrefaction temperatures typically range between 200-320 °C. In the torrefaction process water is removed and cellulose?, hemicellulose and lignins are partially decomposed. The final product is an energy dense solid fuel f e ue tl efe ed to as io- oal. 2. Thermochemical conversion is the application of heat and chemical processes in the production of energy products from biomass. A key thermochemical conversion process if gasification. Gasification Gasification is the use of high temperatures and a controlled environment that leads to nearly all of the biomass being converted into gas. This takes place in two stages: partial combustion to form producer gas and charcoal, followed by chemical reduction. These stages are spatially separated in the gasifier, with gasifier design very much dependant on the feedstock characteristics. Gasification requires temperatures of about 800°C. Gasification technology has existed since the turn of the century when coal was extensively gasified in the UK and elsewhere for use in power generation and in houses for cooking and lighting. A major future role is envisaged for electricity production from biomass plantations and agricultural residues using large scale gasifiers with direct coupling to gas turbines. 3. Biochemical conversion involves use of enzymes, bacteria or other microorganisms to break down biomass into liquid fuels, and includes anaerobic digestion, and fermentation. Anaerobic digestion Anaerobic digestion is the use of microorganisms in oxygen-free environments to break down organic material. Anaerobic digestion is widely used for the production of methane- and carbon-rich biogas from crop residues, food scraps, and manure (human and animal). Anaerobic digestion is frequently used in the treatment of wastewater and to reduce emissions from landfills. Anaerobic digestion involves a multi-stage process. First, bacteria are used in hydrolysis to break down carbohydrates, for example, into forms digestible by other bacteria. The second set of bacteria convert the resulting sugars and amino acids into carbon dioxide, hydrogen, ammonia and organic acids. Finally, still other bacterias convert these products into methane and carbon dioxide. Mixed bacterial cultures are characterized by optimal temperature ranges for growth. These mixed cultures allow digesters to be operated over a wide temperature range, for example, above 0° C and up to 60° C. When functioning well, the bacteria convert about 90% of the biomass feedstock into biogas (containing about 55% methane), which is a readily useable energy source. Solid remnants of the original biomass input are left over after the digestion process. This by-product, or digestate, has many potential uses. Potential uses include fertilizer (although it should Page no: 22 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in be chemically assessed for toxicity and growth-inhibiting factors first), animal bedding and low-grade building products like fiberboard. Fermentation At its most basic, fermentation is the use of yeasts to convert carbohydrates into alcohol – most notably ethanol, also called bioethanol. The total process involves several stages. In the first stage crop materials are pulverized or ground and combined with water to form a slurry. Heat and enzymes are then applied to break down the ground materials into a finer slurry. Other enzymes are added to convert starches into glucose sugar. The sugary slurry is then pumped into a fermentation chamber to which yeasts are added. After about 48-50 hours, the fermented liquid is distilled to divide the alcohol from the solid materials left over. 3. Chemical conversion involves use of chemical agents to convert biomass into liquid fuels. ADVANTAGES 1) Biomass used as a fuel reduces need for fossil fuels for the production of heat, steam, and electricity for residential, industrial and agricultural use. 2)Biomass is always available and can be produced as a renewable resource. 3)Biomass fuel from agriculture wastes maybe a secondary product that adds value to agricultural crop. 4)Growing Biomass crops produce oxygen and use up carbon dioxide. 5)The use of waste materials reduce landfill disposal and makes more space for everything else. 6)Carbon Dioxide which is released when Biomass fuel is burned, is taken in by plants. 7)Less money spent on foreign oil. DISADVANTAGES 1)Agricultural wastes will not be available if the basic crop is no longer grown. 2)Additional work is needed in areas such as harvesting methods. 3)Land used for energy crops maybe in demand for other purposes, such as faming, conservation, housing, resort or agricultural use. 4)Some Biomass conversion projects are from animal wastes and are relatively small and therefore are limited. 5)Research is needed to reduce the costs of production of Biomass based fuels. 6)Is in some cases is a major cause of pollution. Or Advantages of Biomass Energy In many ways, biomass is a new source of power. While wood has always served as a fuel source for fires and ovens and conventional heating methods, biomass energy advancements are a few steps beyond that. Now these biomass fuel products are harvested and mass- produced and used in everything from engines to power plants. 1. No Harmful Emissions: Biomass energy, for the most part, creates no harmful carbon dioxide emissions. Many energy sources used today struggle to control their carbon dioxide emissions, as these can cause harm to the ozone layer and increase the effects of greenhouse gases, potentially warming the planet. It is completely natural, has no such carbon dioxide side effects in its use. Page no: 23 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in 2. Clean Energy: Because of its relatively clean use, biomass energy, when used in commercial businesses such as airlines, receives tax credit from the US government. This is good for the environment and good for business. It does release carbon dioxide but captures carbon dioxide for its own growth. Carbon dioxide released by fossil fuel are released into the atmosphere and are harmful to the environment. 3. Abundant and Renewable: Biomass products are abundant and renewable. Since they come from living sources, and life is cyclical, these products potentially never run out, so long as there is something living on earth and there is someone there to turn that living things components and waste products into energy. In the United Kingdom, biomass fuels are made from recycled chicken droppings. In the United States and Russia, there are plentiful forests for lumber to be used in the production of biomass energy. 4. Reduce Dependency on Fossil Fuels: It has developed as an alternate source of fuel for many homeowners and have helped them to reduce their dependency on fossil fuels. 5. Reduce Landfills: Another benefit of this energy is that it can take waste that is harmful to the environment and turn it into something useful. For instance, garbage as landfill can, at least partially, be burned to create useable biomass energy. 6. Can be used to Create Different Products: Biomass energy is also versatile, as different forms of organic matter can be used to create different products. Ethanol and similar fuels can be made from corn and other crops. With so many living things on the planet, there is no limit to how many ways it can be found and used. Biomass energy power plant Disadvantages of Biomass Energy Besides a o e ad a tages, the e a e also so e do sides to it. Let s see elo so e of its disadvantages. 1. Expensive: Firstly, its expensive. Living things are expensive to care for, feed, and house, and all of that has to be considered when trying to use waste products from animals for fuel. 2. Inefficient as Compared to Fossil Fuels: Secondly, and connected to the first, is the relative inefficiency of biomass energy. Ethanol, as a biodiesel is terribly inefficient when compared to gasoline, and it often has to be mixed with some gasoline to make it work properly anyway. On top of that, ethanol is harmful to combustion engines over long term use. 3. Harmful to Environment: Thirdly, using animal and human waste to power engines may save on carbon dioxide emissions, but it increases methane gases, which are also harmful to the Ea th s— ozone layer. So really, we are no better off environmentally for using one or the other. And speaking of using waste products, there is the smell to consider. While it is not physically harmful, it is definitely unpleasant, and it can attract unwanted pests (rats, flies) and spread bacteria and infection. 4. Consume More Fuel: Finally, using trees and tree products to power machines is inefficient as well. Not only does it take a lot more fuel to do the same job as using conventional fuels, but it also creates environmental problems of its own. To amass enough lumber to power a nation full of vehicles or even a power plant, companies would have to clear considerable Page no: 24 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in forest area. This results in major topological changes and destroys the homes of countless animals and plants. 5. Require More Land: Combustion of biomass products require some land where they can easily be burnt. Since, it produces gases like methane in atmosphere; therefore it can be produced in those areas which are quite far from residential homes. Wind – Energy Fig. 1.3 (A): Wind Power Direct Feed to Main Power line Wind result from air in motion due to pressure gradient. Wind is basically caused by the solar energy irradiating the earth. This is why wind utilization is considered a part of solar technology. Fig. 1.3 (B): Wind Power Direct Feed to Main Power line Energy of wind can be economically used for the generation of electrical energy. Winds are caused from two main factors: 1) Heating and cooling of the atmosphere which generates convection currents. Heati g is aused the a so ptio of sola e e g o the ea th s su fa e a d i the atmosphere. 2) The rotation of the earth with respect to atmosphere and its motion around the sun. Wind mill consists of wind turbine head, transmission and another supporting structure. Wind energy conversion devices like wind turbines are used for converting wind energy into mechanical energy. Wind turbine consists basically of a few sails, vans and blades radiating from a central axis when wind blows against the blades or vans they rotate about the axis. The rotational motion is utilized to perform some useful work. By connecting the wind turbine to an electric generator wind energy can be converted into electric energy. Wind densities upto 10 KW/m3/day are available. More than 20,000 MW electricity can be generated in India from wind. Three factors which determine the output from a wind energy converter: 1. The wind speed. 2. The Cross-section of wind swept by rotor. 3. Conversion efficiency of the rotor transmission system and generator or pump. A. Horizontal axis Page no: 25 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in B. Vertical axis Wind power is the use of air flow through wind turbines to mechanically power generators for electric power. Wind power, as an alternative to burning fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation, consumes no water, and uses little land. The net effects on the environment are far less problematic than those of nonrenewable power sources. Wind farms consist of many individual wind turbines which are connected to the electric power transmission network. Onshore wind is an inexpensive source of electric power, competitive with or in many places cheaper than coal or gas plants. Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher. Small onshore wind farms can feed some energy into the grid or provide electric power to isolated off-grid locations. Wind power gives variable power which is very consistent from year to year but which has significant variation over shorter time scales. It is therefore used in conjunction with other electric power sources to give a reliable supply. As the proportion of wind power in a region increases, a need to upgrade the grid, and a lowered ability to supplant conventional production can occur. Power management techniques such as having excess capacity, geographically distributed turbines, dispatchable backing sources, sufficient hydroelectric power, exporting and importing power to neighboring areas, or reducing demand when wind production is low, can in many cases overcome these problems. In addition, weather forecasting permits the electric power network to be readied for the predictable variations in production that occur. Wind turbines mainly are of two types: vertical axis(VAWT) and horizontal axis(HAWT). HAWT are the most common type of wind turbines built across the world. VAWT is a type of wind turbine which have two or three blades and in which the main rotor shaft runs vertically. They are however used less frequently as they are not as effective as HAWT. The Vertical Axis Wind Turbine (VAWT) is the most popular of the turbines that people are adding to make their home a source of renewable energy. While it is not as commonly used as the Horizontal Axis Wind Turbine, they are great for placement at residential locations and more. Here we will take a look at the VAWT, and fill you in on the pros and the cons as well as other important information that will alleviate stress and headache when you simply want to do your part to keep the environment protected. Ve ti al tu i es spi o the e ti al a is a d o es i a ious shapes sizes a d olo s. It s movement is similar to a coin spinning on the edge. The main difference between the VAWT and HAWT is the position of blades. In HAWT, blades are on the top, spinning in the air while in VAWT, generator is mounted at the base of the tower and blades are wrapped around the shaft. Vertical Axis Wind Turbines are designed to be economical and practical, as well as quiet and efficient. They are great for use in residential areas whereas the HAWT is best for use at a business location. There are two different styles of vertical wind turbines out there. One is the Savonius rotor, and the second is the Darrieus model. The first model looks like a 55 gallon drum that is been cut in half with the halves placed onto a rotating shaft. The second model is smaller and looks much like an egg beater. Most of the wind turbines being used today are the Savonius models. We will take a look more in- depth at both of these types of turbines available. A wind turbine secures air into a hub, which them turns into a generator. The air that passes through the blades of the wind turbine is spun into the generator through rotational momentum. The VAWT, as the turbines are oftener shortened, feature the following qualities: Page no: 26 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in  Two to three blades with a vertically operating main rotor shaft – the more blades that you have on the unit, the more wind energy it will receive and the more efficiency it will offer  Used less frequently than a horizontal wind turbine  The position of the blades is different in the VAWT. On this model, the base of the tower holds the generator, and the blades then wrap themselves around the shaft. People use the VAWT because they can be placed closer to the ground, which makes them acceptable and effective for use at a residential location.  With the vertical axis wind turbine, the rotor shaft is arranged in a vertical pattern  The VAWT are easier and more affordable to maintain than horizontal units  One complain that some users have with the VAWT is that is creates less wind energy, which may cause a number of different noises to be heart. Turbulent air flow is also a possibility that can shorten the life of the system.  Installation of the VAWT onto the roof will cause the wind speed to double for maximum wind turbulence and wind energy usage. Types of Vertical Axis Wind Turbines there are two different types of VAWTs that you can choose from. While we looked at these types briefly above, now we will take a look at more information about each type and discuss the i po ta t fa to s that ou should k o. Fi st, let s take a look at the Darrieus wind turbine mode. Darrieus Wind Turbine Darrieus Wind Turbine is o o l k o as a Egg eate tu i e. It as i e ted Georges Darrieus in 1931. A Darrieus is a high speed, low torque machine suitable for generating alternating current (AC) electricity. Darrieus generally require manual push therefore some external power source to start turning as the starting torque is very low. Darrieus has two vertically oriented blades revolving around a vertical shaft. The Darrieus wind turbine offers the following features:  These eggbeater shaped turbines are great at efficiency, however, they are not as reliable.  In order to use the Darrieus wind turbine you must have an outside source of power in order to start them  It is in your best interest to choose a wind turbine that has at least three blades.  To support such a wind turbine it is necessary that you have a superstructure which will connect it near the top bearing. Savonius Wind Turbine: A Savonius vertical-axis wind turbine is a slow rotating, high torque machine with two or more scoops and are used in high-reliability low-efficiency power turbines. Most wind turbines use lift generated by airfoil-shaped blades to drive a rotor, the Savonius uses drag and therefore cannot rotate faster than the approaching wind speed. Now let s take a look at the se o d t pe, hi h is also the ost popula of the t o. The “a o ius i d tu i e is the ost popula of the t o t pes. Let s go ahead a d look at so e of the features these VAWT offer to the homeowner.  As a drag type of turbine, these units are less efficient.  When you live in an area that has strong and gusting winds or when you need a unit that self-starts, this is the best type available to you.  This unit is larger than the Darrieus model. Page no: 27 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in Savonius vertical axis wind turbine needs to be manually started. The slow speed of Savonius increases cost and produces less efficiency. Advantages of Vertical Axis Wind Turbines You might be wondering why you would consider using a VAWT instead of a HAWT. There are a tuall a u e of easo s that this de isio is ade. Let s take a look at so e of the advantages that you can enjoy with this type of wind turbine in use at your home.  You can build your wind turbine close to the ground so if you do not have a suitable rooftop for placement, or if you live where there are hills, ridges, etc. that prohibit the flow of air, they work wonderfully for your needs.  Since VAWT are mounted closer to the ground they make maintenance easier, reduce the construction costs, are more bird friendly and does not destroy the wildlife.  You do not need any mechanisms in order to operate the wind turbine  Lower wind startup speed  The main advantage of VAWT is it does not need to be pointed towards the wind to be effective. In other words, they can be used on the sites with high variable wind direction.  You can use the wind turbine where tall structures are not allowed.  VAWT s a e uiet, effi ie t, e o o i al a d pe fe t fo eside tial e e g production, especially in urban environments.  They are cost effective when compare to the HAWTs. It is still best to shop around and check prices before making a purchase, however.  Many of the turbines are resistant to many of the different weather elements that you may experience. It is imperative to choose a unit that offers this valuable protection and extra durability when you need it the most. Disadvantages of Vertical Axis Wind Turbines There are also disadvantages that come with the use of this type of wind turbine. While the many advantages are certainly great, it is imperative that you are aware of the disadvantages. Before deciding which type of wind turbine is best for you it is good idea to take a look at both the pros and the cons. What is right for one person may not be right for you, although it is safe to say that a VAWT is great for almost any residential setting. Let s take a look at so e of the disad a tages of usi g a VAWT:  Decreased level of efficiency when compared to the HAWT. The reason for the reduced amount of efficiency is usually due to the drag that occurs within the blades as they rotate.  You are unable to take advantage of the wind speeds that occur at higher levels.  VAWT s a e e diffi ult to e e t o to e s, hi h ea s the a e i stalled o base, such as ground or building. Solar energy Solar panels converts the sun's light in to usable solar energy using N-type and P-type semiconductor material. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is Page no: 28 Follow us on facebook to get real-time updates from RGPV Downloaded from be.rgpvnotes.in called the photovoltaic (PV) effect. Currently solar panels convert most of the visible light spectrum and about half of the ultraviolet and infrared light spectrum to usable solar energy. Solar energy technologies use the sun's energy and light to provide heat, light, hot water, electricity, and even cooling, for homes, businesses, and industry. There are a variety